The phenomenon you are referring to is showing the effect that prevailing culture has on an individual's personal morality. See also the difference between American Christians and Christians in other parts of the world (or more pertinently, different areas of the U.S. itself). It has nothing to do with "political correctness" and everything to do with cultural and societal values.
I agree but to me I am not sure why atheists bother having morals since they change them all the time. BTW this can apply to chrsitians too. How can something be moral if your constantly shifting your view on it. Today killing is bad, tomorrow its not, the next day its bad again. Granted that an overblown example for example sake.
I'm someone that believes stand for what you believe in and NEVER change your mind on it. Especially as a christian where our morals have already been told to us on how we should view things. Id rather die fighting for what I believe then to compromise. Because once you start compromising and changing, then you can't be taken seriously.
One example is in marriage. If I dated a woman who lets say her whole life believed looking at porn was a sin, but then suddenly changed her mind on it. I would dump her and never talk to her again. If she can change her mind on one thing (a thing we know is a sin), whats to stop her from changing her mind once married about things like divorce, cheating, spending alot of money...etc. I have no trust in people who change their mind and morals all the time.
Mind you I am referring to changing their mind on important things like if porns a sin or not. I'm not referring to things like someone deciding to eat a burger instead of a hotdog obviously.
Actually as I think about this. I remember many atheists say christians are weak and robots and its why they cling to religion. But technically aren't atheists the same "weak robots"? They let the world and culture decide whats moral for them. THey follow it blindly when it becomes popular opinion. They may say "But things like science are what we go by...logic!". But thats always changing which means you are also. So therefor you follow something to.
Technically this could turn into that other topic about is science a religion.

Glad to know until the day I die my beliefs won't change. Thats not to say they won't teeter on the edge like if I had something tragic happen to me.